1. Field of the Invention
The invention relates to a rotating machine grinding tool. In particular, the invention relates to a grinding tool that comprises a carrier body in the form of a disk which has a working side equipped with a grinding element. The disk can be attached to a machine drive by means of a connection element located in about the area of the center of rotation.
2. The Prior Art
Grinding machines are used to grind profiled surfaces of workpieces. It is known to mold into the working sides of such machines contours negatively corresponding with the contour of the profile that is to be ground. An abrasive agent is then attached or glued to the contoured working side in order to grind the workpiece. So as to avoid so-called xe2x80x9cburningxe2x80x9d caused by extreme frictional heat at a higher grinding contact pressure, it has previously been proposed to arranged a cushioning layer, for example a layer made of an elastic, cellular foam material, between the working side and a grinding linen. Relatively soft grinding can be effected in this way, which may be suitable even for grinding lacquer, if need be.
Particularly when equipped with a cushioned grinding element, the working side also may more or less adapt itself to variations in the shape of the workpiece depending on the grinding pressure. However, this adaptation is limited by the elasticity of the cushioning layer used, and also by the elasticity of the material employed for the carrier body or the area of its working side. For example, the areas of transition or connection of assembled workpieces often comprise surfaces that are difficult to grind. Such difficulty is present particularly in cases where the workpiece is a profile, or comprises sections adjoining each other within the zone of connection at a predetermined angle. This is often the case in conjunction with staircase railings.
Such zones can often be ground only by hand using suitable grinding elements such as grinding linen, abrasive paper or the like, in a labor-intensive manner.
The invention addresses the problem of providing a grinding tool that can be easily used and applied for many different purposes, and applied in conjunction with suitable machines even if difficult configurations need to be ground in difficult spots as well.
The problem is solved according to the invention by providing a grinding element in the form of a disk leaf, i.e. a thin or leaf-like disk that is set radially in relation to the axis of rotation, and whose periphery protrudes beyond the outer edge of the working side of the carrier body by a predetermined amount.
When the carrier body is rotating, grinding can be carried out with the disk leaf, which is disposed radially in relation to the axis of rotation, by guiding the abrasive side of the disk leaf that is facing away from the working side of the carrier body, across the surface of the workpiece to be ground, like a grinding wheel. This can be accomplished by freely guiding a connected, corresponding machine drive by hand.
The grinding element takes the form of a relatively thin and, therefore leaf-like disk. The centrifugal forces caused by the rotation stretch the grinding element, and such stretching stiffens the grinding element. Nevertheless, the area of the grinding element that clears or freely projects beyond the outer edge of the working side of the carrier body remains yielding or flexible versus the forces acting transversely in relation to the plane of rotation. The freely protruding portion will yield to projections on the workpiece during rotation. In this way, the grinding contact pressure required for grinding the workpiece projection will be maintained without increasing that contact pressure to an undesirable order of magnitude.
The grinding tool as defined by the invention does not comprise any fixed support flange for the actual abrasive coating that is applied to the surface of the disk leaf. Advantageously, this feature makes it possible for the abrasive coating, which remains highly flexible, to grind three-dimensional configurations, planes and transitions in shape without any problems. Grinding of such structures has been possible heretofore only by means of the so-called freehand grinding method, in which process a grinding means, for example abrasive paper placed around a hand-held block element, is both moved and guided by hand, i.e. manually. The machine grinding tool as defined by the invention consequently can be operated in a variable manner accordingly, like the grinding device used in free-hand grinding operations; however, with substantially superior grinding efficiency and better grinding results.
The machine grinding tool as defined by the invention is capable of grinding in all areas of deformed planes. The tool is also able to grind in all areas of transition in the configuration, or areas of transition between individual components. In each case, the tool grinds with a constant contact pressure and has as a special advantage, the optimal contact pressure resulting from soft grinding.
It is very important in connection with the grinding tool as defined by the invention that the supporting elements, in the present case the carrier body with its connecting elements, have a much smaller diameter than the grinding element, i.e. the disk leaf. The dimensional stability of the disk leaf is achieved solely by the centrifugal force generated at a predetermined rotational speed. The selected diameters permit deformation over a large area in the actual grinding plane. This feature makes it possible to readily grind difficult configurations of a workpiece.
It is particularly advantageous if the disk leaf comprises at least two disk layers resting against one another. A first layer of the disk is a layer of an elastic cushion and a second layer is a highly flexible grinding linen. Both layers are circular rings punched from suitable materials. Such circular rings are attached to each other by suitable measures for joining them, for example by gluing. The outside diameter of the second layer consisting of highly flexible grinding linen is dimensioned in such a way that it freely projects to a predetermined extent beyond the outer edge of the first layer, which is the elastic cushioning layer.
This embodiment offers the advantage that the elastic cushioning layer jointly supports the inner areas of the grinding tool. These areas are located adjacent to the center of rotation where the centrifugal forces cannot exert the same stiffening effect as they do along the periphery. The elasticity of this cushioning layer leads to soft grinding action in these areas as well even though these areas are located close to the axis of rotation.
The predetermined amount by which the outer edge of the second layer of the disk leaf clears or freely protrudes beyond the outer edge of the first layer of the disk leaf, which is the cushioning layer, is at least equal to the thickness of the cushioning layer. With a thickness of the cushioning layer of, for example 3 mm, the outer edge of the second layer of the disk leaf freely projects beyond the outer edge of the first layer by 5 mm in a preferred embodiment. Therefore, in this embodiment, the outer edge of the second layer projects by more than the thickness of the cushioning layer.
According to an advantageous embodiment, the carrier body takes the form of a disk ring as well, which is so thin that its peripheral area is capable of elastically yielding transversely to the plane of the disk ring. In this embodiment, the disk ring has an attachment for the connecting element that is located in the center of the disk ring. The shape and form of this attachment are selected so that the attachment of the carrier body is in the form of a sleeve, whereby the disk ring corresponds with a collar flange projecting from the sleeve in an approximately radial manner.
The grinding element may be connected with the carrier body by gluing its cushioning layer to the thin and therefore elastic collar flange. The carrier body is preferably a single-piece, molded component made of glass fiber-reinforced polyamide. This material possesses high strength on account of its glass fiber reinforcement and also exhibits adequate elasticity by dimensioning the collar flange so that it is approximately equal to one twentieth of its width. It is also advantageous, furthermore, that this material can be caused to slightly start to dissolve with defined solvents, so that the grinding element can be readily glued to a surface starting to dissolve. No additional adhesive is needed.
The carrier body equipped with the grinding element is a favorably priced disposable component that can be simply replaced when it is worn. Carrier bodies made of glass fiber-reinforced polyamide can be manufactured as mass-produced articles in the injection molding process. The grinding elements can be produced in series on the industrial scale as well. With the grinding tool of the present invention, it is no longer necessary to mold the negative form of the profile to be ground into the working sides of grinding tools in order to work in defined profiles in contour grinding operations.
The grinding element present in the form of a disk leaf has a hole in the center, the diameter of which is about equal to, but not less than the outside diameter of the sleeve of the carrier body. Thus the grinding element with the hole can be plugged over the sleeve of the carrier body, whereby it is glued to the sleeve with its cushioning layer resting against the collar flange.
The outside diameter of the elastic cushioning layer of the grinding element present in the form of a disk is approximately equal to three times the width of the collar flange of the carrier body. The thickness of the elastic cushioning layer is approximately equal to three times the thickness of the collar flange as well. With an outside diameter of the collar flange of, for example 70 mm, and a width of about 10 mm, the collar flange has a thickness of about 1 mm.
Thus the collar flange is a highly elastic, springy component supporting the grinding element in the center. Such support grows gradually softer in the direction of the outside diameter of the collar flange and thus over the radial spacing from the center of rotation. This arrangement is desirable for achieving optimal grinding results with the grinding tool as defined by the invention as well. The grinding tool according to the invention permits grinding sharp-edged corners. The elasticity of its grinding element prevents flat grinding contours from occurring on curved workpieces due to excessive grinding pressure. Transitions of surfaces on workpieces are simultaneously ground as well because the grinding element nestles itself to all planes in the transition area. The relatively soft grinding element of the grinding tool as defined by the invention prevents undesirable heat from building up, for example when grinding workpieces made of stainless steel. Such materials could otherwise cause undesirable discoloration of a workpiece due to frictional heat.